code: def test_pandas_anchor():
      # Test that anchor with dates works
      ix = pd.date_range(start="2000", periods=10, freq=MONTH_END)
      endog = pd.DataFrame(np.zeros((10, 2)), index=ix)
      mod = TVSS(endog)
      res = mod.filter([])
  
      desired = res.impulse_responses(2, anchor=1)
  
      # Anchor to date
      actual = res.impulse_responses(2, anchor=ix[1])
      assert_allclose(actual, desired)
      assert_(actual.index.equals(desired.index))
  
      # Anchor to negative index
      actual = res.impulse_responses(2, anchor=-9)
      assert_allclose(actual, desired)
      assert_(actual.index.equals(desired.index))
  
imports: from statsmodels.compat.pandas import MONTH_END
  import warnings
  import numpy
  from numpy.testing import assert_, assert_allclose
  import pandas
  import pytest
  from scipy.stats import ortho_group
  from statsmodels.tools.sm_exceptions import EstimationWarning
  from statsmodels.tsa.statespace import dynamic_factor, mlemodel, sarimax, structural, varmax
  from statsmodels.tsa.vector_ar.tests.test_var import get_macrodata
label_desc: Use image node_id 15 for calling a global function with example usage: test_pandas_anchor() without return types